Nope. And I'd not work anywhere that did. As for music? My absolute faves are alternative ambient dubstep electronic experimental indie instrumental post rock progressive rock psychedelic psytrance shoegaze twee but I like tons of other stuff as well.

I'm not sure I understand why companies restrict it - for most people, usage will be something like posting a quick message or IM a few times an hour (so about the same amount of time spent as people going for cig/water cooler breaks). Plus, no one really has 100% productivity except in the very short term, as that tends to result in burnout and stress. A bit of case of diminished returns!